Vacuum-press molding

Preform. A metal screen is made in the shape of the final product. Glass fiber is chopped 2 in. long and sprayed uniformly all over the shaped screen, using vacuum on the back side of the screen to assist the process. A small amount of binder, typically 5 percent of polymer in latex form, is sprayed onto the fiber to hold its shape. It is then removed from the screen, placed in the mold, saturated with an equal weight of liquid resin, and the mold is pressed at 1380 kPa (200 psi) and heated until cured, typically 3-15 min. This early process has been largely replaced by SMC. 

Compression Molding Flexible Plunger Flexible Bag Molding Laminate Hand Lay-Up Vacuum Bag Molding Vacuum Bag Molding and Pressure Pressure Bag Molding Autoclave Molding Autoclave Press Clave Wet Lay-Up... 

VCEMA vinyl chloride-ethylene-methyl acrylate VPM vacuum-press molding... 

The composites made with hand lay-up technique. Short fibres with weight fraction 30% and 50% for eacth length mixed with the rain and then put in a vacuum jar and degassed until "boiled" and all bubbles in the resin are remove. After that poured the mixture to the mold, spacer were used in order to produce 2 mm thick of composite. The mold was press with 20 N/cm. Cured was carried out at room temperature for 16 hours and then post curing was done in an air oven at 80 0 for 5 hours. 

Cure types are indicated as a = autoclave, c = compression molding, p = press, v = vacuum bag. High temperature grades up to 260°C/500 F. 

Vacuum mold cavity Press can include a vacuum chamber around or within the mold providing removal of air and other gases from the cavity(s). 

Billow drape forming consists of a male mold pressed into a sheet prestretched by the billowing process (Fig. 1.74). A similar process is billow vacnnm forming, wherein a female mold is used (Fig. 1.75). In vacuum snap-back forming, vacnnm is nsed to prestretch the sheet, then a male mold is pressed into the sheet, and, finally, pressnre is nsed to force... 

In addition to providing sufficient space for the mold, the press must include space for a pressure box and other elements, such as plug assist plates, cavity isolator plates, trim-in-place die plates, and ejector-ring plates. Water and vacuum lines should be properly located and should be easy to disconnect. Programmable logic controls are needed for adjustment of all rate-dependent ancillary features, such as plug assist, cavity isolator, pressure box, and trim-inplace sequence. Many newer machines are equipped with computer controls that provide for rapid setup after mold changeover. The press platens must allow easy mold removal and installation. 

A different type of inspection is needed for the re-installation of a mold that has been in storage for some time. Even though the mold assembly— the mold, its vacuum box, plug plate, plugs, air and coolant line quick disconnects, and its pressure box—may have been stored as a single unit, often bits and pieces are scavenged for other molds. Installation may be delayed until the missing pieces are found or replaced. The same is true with trim dies, trim fixtures, and elements of stackers. It is vital that the mold and press set-up protocols are stored with the mold. If these are stored electronically on a disk or chip, a paper printout of the access codes to the protocols is required to ensure that the appropriate software is available. An example of the product should also be placed in the mold cavity. 

The beater additive process starts with a very dilute aqueous slurry of fibrous nitrocellulose, kraft process woodpulp, and a stabilizer such as diphenylamine in a felting tank. A solution of resin such as poly(vinyl acetate) is added to the slurry of these components. The next step, felting, involves use of a fine metal screen in the shape of the inner dimensions of the final molded part. The screen is lowered into the slurry. A vacuum is appHed which causes the fibrous materials to be deposited on the form. The form is pulled out after a required thickness of felt is deposited, and the wet, low density felt removed from the form. The felt is then molded in a matched metal mold by the appHcation of heat and pressure which serves to remove moisture, set the resin, and press the fibers into near final shape (180—182). 

The rigidi d thermoplastic sheet - Tiocess combines thermoplastic sheet vacuum forming with a spray-up or cold press molding process to add a thermoset composite stmctural backing to a decorative thermoplastic skin. Large parts such as bathtubs, hot tubs, recreation vehicle components, and camper tops have been produced by this process. 

Figure 19 illustrates one type of compression mold suitable for molding lip type shaft seals with a metal outside diameter (O.D.). Figure 19a shows the compound preform resting on the shelf and the mold beginning to close. The mold continues to close until it gets to the position shown in Fig. 19b. Finally, the mold opens as shown in Fig. 19c. It can be seen that this molding technique produces a molded lip seal with the flash already removed. In general, when using a vacuum chamber on the press, to ensure that all the air and/or gases are evacuated from the mold after closure, one or...

Polymer Processing. Polymer films were cast in trimethylsilyl coated glass molds from membrane filtered 15% (w/v) methylene chloride or chloroform solutions. Transparent films were obtained which were dried to constant weight in high vacuum. Rectangular strips or round disks were cut from the films. For compression molding a Carver laboratory press equipped with thermostated, heated platens was used. Polymers were placed in a stainless steel mold and heated to 40 °C above their glass transition temperature. Then a load of 1-2 tons was applied for 5 min. 

Sample Preparation. Samples for mechanical studies were made by compression molding the polymers at 150°C between Teflon sheets for 15 minutes followed by rapid quenching to room temperature in air. These will be referred to as PQ (press-quenched or simply quenched) samples. The thickness of the PQ samples was around 10 mils (0.25 mm). The thermal history of all of the PQ samples (HBIB, HIBI, and LDPE) were essentially the same. They were used within one week after they were pressed. Samples for morphology, SALS and SEM studies were prepared from toluene solutions. These films were cast on a Teflon sheet at 80 C from a 1% (by weight) solution in toluene. These films were about 5 mils in thickness. When the polymer films had solidified (after 5 hrs), they were stored in a vacuum oven at 80°C for two days to remove residual solvent. These samples will be designated by TOL (solution cast from toluene). 

In pressure-bubble vacuum snapback, the heated sheet is clamped and sealed against a pressure box. Air is forced through the female pressure box forcing the sheet to push outward from the pressure box. A male mold is then pressed against the bubble and as it pushes into the pressure box, excess air is forced from the pressure box forcing the heated sheet to take the shape of the male mold. The major difference between the vacuum snapback and pressure-bubble vacuum snapback is that in the vacuum snapback process vacuum from a female... 

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